1. Field of the Invention
The present invention relates to a novel optically active azo compound, a producing method thereof, and a liquid crystal composition containing said compound.
2. Description of the Related Art
Each of liquid crystal materials is widely used as an element for a display at the present time. These liquid crystal display elements are almost constructed by a display system of a twisted nematic type (TN-type) using a nematic liquid crystal. This display system has many merits and advantages. However, responsibility of the display system is very low in comparison with that of a display system of a light emitting type such as a CRT. No responsibility can be easily improved although many liquid crystal display systems except for the display system of the TN-type are also considered.
However, a liquid crystal device using a ferroelectric smectic liquid crystal has a high response speed 100 to 1000 times that of the general liquid crystal display element of the TN-type. Further, this liquid crystal device has preferable bistability. Accordingly, displayed contents are memorized even when a power source of the liquid crystal device is turned off. Such a memory effect has been recently found. Therefore, there is a high possibility that such a liquid crystal device can be used for an optical shutter, a printer head, a thin type television, etc. The liquid crystal device is searched and developed at the present time to practically use this device in various kinds of industrial fields.
A phase of the ferroelectric liquid crystal belongs to a chiral smectic phase of a tilting system. A practically desirable liquid crystal phase of the ferroelectric liquid crystal is a so-called chiral smectic C-phase having low viscosity.
For example, the following properties are required with respect to such a ferroelectric liquid crystal material.
(1) The ferroelectric liquid crystal material is chemically stable and has excellent durability.
(2) The ferroelectric liquid crystal material has a wide liquid crystal phase in a temperature range from a low temperature to a high temperature and shows ferroelectricity in a wide temperature range including a room temperature.
(3) The rotational viscosity of a liquid crystal molecule in the ferroelectric liquid crystal material is small and the ferroelectric liquid crystal material has large spontaneous polarization and high speed responsibility.
For example, various kinds of liquid crystal compounds are already synthesized on the basis of such material designs in Japanese Patent Application Laying Open (KOKAI) Nos. Hei 2-225441 and Hei 2-229131, etc. However, at the present stage, it is difficult to obtain a practical material constituting a ferroelectric liquid crystal constructed by a single composition and satisfying the above-mentioned various properties. Similar to the case of a nematic liquid crystal already used practically, there is a trial for obtaining desirable characteristics for the ferroelectric liquid crystal by mixing several kinds of compounds with each other.